Just come back from a 7-night cruise to Eastern Caribbean, and had a great time.
The ship (at time of writing) is still less than a year old, and is shiny and new, with all the carpets still spotless, and the marble and gold railings gleaming, the cabin still fresh, the bed still comfortable. Had a balcony stateroom up on deck 15, and forward, so I was a little apprehensive about feeling too much of the swell once we got out onto open waters ... but we never felt anything worse than a gentle rocking (though that might not be the case if Regal Princess ventures out into the mid-Atlantic, say). Staff were always friendly and courteous, food in the buffet was good, and sometimes very good; in the restaurants, very good and sometimes excellent.
Sailed on the Crown Princess to Norway a couple of years ago - and was very disappointed with the catering arrangements on that occasion, because there never seemed to be an open table to sit down at when we visited the buffet - but the Regal seems to have more floorspace for the buffet, so this is never a problem!
The onboard entertainment was excellent - again, much better than on the Crown.
The only thing I found less than satisfying was the stop at Princess Cays island - it's way too small a beach for the 4,000 people aboard the Regal, the catering on the island was low-budget, and the sand underfoot, when you try swimming or snorkelling, is rocky and sharp. And there's nothing there for snorkelers to see, anyway!
That aside ... it's a great trip, on a great ship. highly recommended!